Mold for continuous casting of strands

ABSTRACT

A mold for continuous casting of strands and including a pouring spout, and a housing surrounding the pouring spout and spaced from the pouring spout, forming with the pouring spout a gap that provides for flow of cooling medium therethrough, with the gap having a small width in an upper mold region and a relatively large width in a lower mold region.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a mold for continuous casting ofstrands, in particular billet or bloom strands, and including a pouringspout, and a housing surrounding the pouring spout at a distancetherefrom, forming with the pouring spout a gap that provides for flowof cooling medium therethrough.

[0003] 2. Description of the Prior Art

[0004] During continuous casting of metals, in particular duringcontinuous casting of steel, the liquid steel solidifies, in the courseof the casting process, in a continuous casting mold from abovedownward. The solidification takes place approximately hyperbolically inaccordance with an equation

s=k×{square root}{square root over (t)}, wherein

[0005] s is a thickness of the strand shell;

[0006] k is a cooling coefficient; and

[0007] t is time.

[0008] In order to provide for the above-determined solidification curvealready in the continuous casting mold, the heat removal from the moldcan be regulated by controlling local water flow velocities. The maximalheat removal should take place in the meniscus of the mold bath mirror.At the outlet of the mold a correspondingly smaller amount of heat isremoved.

[0009] German Publication DE-OS 14 83 556 discloses distribution ofcooling zones along the mold height, with the zones being located oneabove the other and with each cooling zone having its own delivery andremoval conduits.

[0010] German Patent No. 1.608,059 discloses flow of a cooling medium invertical channels from beneath upward through the cooling boxes of themold, with a high counter pressure.

[0011] An object of the present invention is to provide a mold forcontinuous casting of strands and in which, the flow velocity of thecooling medium in the cooling channels of the cooling jacket of the moldis controlled by selecting an appropriate geometry of the cooling mediumguiding jacket.

SUMMARY OF THE INVENTION

[0012] This and other objects of the present invention, which willbecome apparent hereinafter, are achieved by providing a gap having asmall width in an upper mold region and corresponding to a high coolingmedium velocity, and a relatively large width in a lower mold region andcorresponding to a relatively low velocity of the cooling medium.

[0013] Thus, according to the present invention, the water flow velocityand, thereby, the removal of heat is controlled by an appropriateselection of the geometry of the cooling medium channel.

[0014] According to the present invention, at least a vertical profileof the outer wall of the cooling medium wall corresponds to a reverseshape of a solidification line in the cast strand running from abovedownward. The reverse shape results in low cooling medium velocities inthe lower region of the mold and in high cooling medium velocities inthe upper region of the mold which are caused by the narrowing of thegap.

[0015] A further improvement in the geometry of the cooling medium gapis achieved by additionally increasing its size in its corner regions.Because the corners of a strand require less heat removal than thesurfaces of the strand, the cooling medium flow velocity can be reducedin the corner regions of the gap.

[0016] According to the present invention, the gap has a different widthalong at least one of wide side of the mold and longitudinal side of themold with a narrowest width being provided in a middle of the at leastone of wide side and longitudinal side. By providing the smallest widthin the middle of a respective side or sides, an increase of the coolingmedium flow velocity is achieved in this region in comparison withcorner regions. The reduced velocity in the corner regions is obtainedas a result of providing a bulged profile in this regions.

[0017] Forming the pouring spout according to the present invention as acylindrical member simplifies the manufacturing of the mold.

[0018] A favorable flow, with a reduced flow resistance, is achieved byforming the corner regions, in a horizontal plane, with an oval-shapedbulging profile.

[0019] The novel features of the present invention, which are consideredas characteristic for the invention, are set forth in the appendedclaims. The invention itself, however, both as to is construction andits mode of operation, together with additional advantages and objectsthereof, will be best understood from the following detailed descriptionof preferred embodiments, when read with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the Drawings:

[0021]FIG. 1 a vertical cross-sectional view of a mold for continuouscasting according to the present invention; and

[0022]FIG. 2 a horizontal cross-sectional view along line A-A in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] A mold for continuous casting according to the present inventionwhich is shown in FIGS. 1-2, is used in particular for casting billetand bloom strands. The mold includes a pouring spout 1 and a moldhousing 2 which form together a water jacket 2 a. The cooling medium 4,usually water or water with additives, is fed through a vertical coolingmedium gap 5 between the pouring spout 1 and the housing 2 and, afterbeing heated upon rising, is removed. As shown with arrows in FIGS. 1-2,the cooling water is introduced into the gap 5 at the lower mold region6 b and is removed at the top or upper mold region 6 a.

[0024] According to the present invention, the width of the coolingmedium gap 5 changes along the mold height. As shown in the drawings,the width of the cooling medium gap 5 narrows toward the top of themold, leading to an increase of cooling medium velocity in the upperregion 6 a of the mold. In the lower mold region 6 b, the cooling mediumgap 5 is relatively wide which results in a relatively small velocity ofthe cooling medium in the lower region 6 b of the mold. The flowvelocity of the cooling medium 4 corresponds to a reversed shape of thesolidification line in the cast strand and to the profile 7 (FIG. 1) ofthe inner wall 5 a of the mold housing 2 defining, together with theouter wall of the pouring spout 1, the cooling medium gap 5.

[0025] As shown in FIG. 2, the cooling medium gap 5 has increaseddimensions in corner regions 8. The cooling medium gap 5 can have adifferent width along the mold wide side 9, the mold longitudinal side10, and along both the mold wide side 9 and the mold longitudinal side10, with the narrowest width 11 being provided in the middle 12 of thewide or/and longitudinal side(s).

[0026] The pouring spout 1 can be easily and precisely produced becauseonly the mold housing 2 has a changing profile 7. The formation of thecorner regions 8 with respective oval profiles 13 (in the horizontalprojection) also does not affect the profile of the pouring spout 1.

[0027] The respective gap width follows the functions gap width=f(h)according to FIG. 1, and gap width=f(x) according to FIG. 2.

[0028] Though the present invention was shown and described withreferences to the preferred embodiment, such are merely illustrative ofthe present invention and are not to be construed as a limitationthereof, and various modifications to the present invention will beapparent to those skilled in the art. It is, therefore, not intendedthat the present invention be limited to the disclosed embodiment ordetails thereof, and the present invention includes all of variationsand/or alternative embodiments within the spirit and scope of thepresent invention as defined by the appended claims.

What is claimed is:
 1. A mold for continuous casting of strands,comprising a pouring spout; and a housing surrounding the pouring spoutat a distance therefrom, forming with the pouring spout a gap thatprovides for flow of cooling medium therethrough, the gap having a smallwidth in an upper mold region and corresponding to a high cooling mediumvelocity, and a relatively large width in a lower mold region andcorresponding to a relatively low velocity of the cooling medium.
 2. Amold as set forth in claim 1, wherein at least a vertical profile of aninner wall of the mold housing, which defines an outer wall of the gap,has a shape corresponding to a reverse shape of a solidification line ina cast strand running from above downward.
 3. A mold as set forth inclaim 1, wherein the gap for cooling medium is increased in cornerregions thereof.
 4. A mold as set forth in claim 1, wherein the gap hasa different width along at least one of wide side of the mold andlongitudinal side of the mold, with a narrowest width being provided ina middle of the at least one of wide side and longitudinal side.
 5. Amold as set forth in claim 2, wherein the pouring spout is formed as acylindrical member.
 6. A mold as set forth in claim 3, wherein thecorner regions have, in a horizontal plane, an oval-shaped, bulgingprofile.